Cambrian Embryo Fossil (image) University of Missouri-Columbia Caption This is a Cambrian embryo fossil exposed by acid etching on rock surface. Polygonal structure on surface indicative of blastula-stage of development. Credit Broce, et al. Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.